Casting mold for fabricating a flexible product

ABSTRACT

A mold for casting solidifiable materials and method of fabricating a continuous belt from molded sections is disclosed. In the mold, a plurality of apertures are provided in a special pattern, each of which is adapted to receive a core member. The core members are easily removable. Removable end plates are provided which enable the pattern to be continued to the very edge of the mold. A continuous belt mold is fabricated by butting and connecting edges of molded sections.

United States Patent [15] 3,695,573 Huffaker et a]. [451 Oct. 3, 1972[54] CASTING MOLD FOR FABRICATING A 3,482,326 12/1969 Brewster ..249/176 X FLEXIBLE PRODUCT FOREIGN PATENTS OR APPLICATIONS [72] Inventors:James E. Huffaker, Kingsport,

Tenn; Ernest Myers, Hilton, 862,705 3/1961 Great Britain ..249/176 BrianD. Dillon; Cecil W. Dolen, both of Kingsport, Tenn. j g -tfig tgverholser szstant ammeruclus rye [731 Ass1gnee= Eastman Kodak Company,AttorneyDa.niel J. Hanlan, Jr., William D. Herrick Rochester and RaymondJ. Miller [22] Filed: June 1, 1970 5,7 ABS CT 211 App]. No.: 42,106 l 1v A mold for casting solidifiable materials and method r of fabricatinga continuous belt from molded sections [22] :LSSI. ..249/142, 249/176326477212 is disclosed In the mold, a plurality of apertures are dprovided in a special pattern, each of which is adapted 1 o rc I i 1% 2to receive a core member. The core members are easi- I 1y removable.Removable end plates are provided which enable the pattern to becontinued to the very [56] References cued edge of the mold. Acontinuous belt mold is fabricated UNITED STATES PATENTS by butting andconnecting edges of molded sections.

3,290,421 12/ 1966 Miller .l ..249/176 X 4 (Ilaims, 5 Drawing Figures E/72 28 32 Q 39 32 7o 32 1?- PATENTEflucra 191 2 SHEET 1 BF 2 JAMESE.'HUFFAKER ERNEST L. MYERS BRIAN D. DILLON CECILEW. DOLEN mv NTO BY 4am4&

ATTORNEY PATENTEDnm I912 3.695.573

I SHEET 2 UF 2 JAMES E.HUFFAKER ERNEST L.MYERS BRIAN D.D|LLON CECIL w.DOLEN INVENTQRS ATTORNEY CASTING MOLD FOR FABRICATING A FLEXIBLE PRODUCTThis invention relates generally to molds for casting materials andthereafter fabricating a continuous product therefrom. Moreparticularly, this invention relates to a male mold from which a femalemold section is made, and the fabrication of a continuous female moldfrom cast sections thereof.

The casting mold according to the present invention is useful in themanufacture of continuously molded sheet material, such as for example,a continuous sheet of thermoplastic material molded into a three-dimensional product having a multiplicity of closely spaced cells formedtherein with sidewalls extending substantially perpendicular to theplane of the product.

In the past, much difficulty has been encountered in such molds due tosuchrequirements as durability, flexibility, economy, and the like. Forproducing a continuous product on an endless belt-type mold, the moldmust have the flexibility and durability to flex many times in passingaround rolls over which it is entrained. In such flexing, it isimperative that fractures of the mold must not occur, else a defect inthe molded material will occur at the point of fracture. Furthermore, amajor problem occurs in attempting to fabricate a continuous mold,because if it is attempted in a continuous casting operation, the molditself would necessarily have to be flexible. In casting sections of themold to subsequently be pieced together, difflculty has been encounteredin exact matching of the pattern at the joints of the individualsections.

In the molding of patterns of delicate features,

problems have also been encountered in the incorporation of the delicatefeatures into the mold. When the pattern is repetition of a multiplicityof intricate details, the problem also is multiplied. Intricate detailsshould not be too difficult or costly to incorporate into the mold.Furthermore, the possibility of damage to the mold details must beconsidered, and if such occurs, replacement of individual sections mustbe economical and relatively simple.

The mold musthave the ability to withstand relatively high moldingtemperatures as well as numerous and rapid temperature fluctuationswithout undue dimensional changes or fracturing. Moreover, the intricatedetails of pattern must be precision-made and fitted so there is nopossibility of flashing which might make the molded article difficult tostrip from the mold.

The present invention provides a male mold for casting female sectionsof a second production mold of intricate repeating patterns which can bepieced together to make a durable, flexible continuous pattern withsubstantially no interruption in the pattern. The present inventionfurther provides a method of piecing these sections together to form acontinuous belt-type mold.

According to the present invention, a base plate is drilled to form aplurality of parallel rows of apertures, the apertures in each row beingsubstantially equally spaced and the apertures in alternate rows beingstaggered with respect to the apertures in adjacent rows and in generalalignment with the apertures in alternate rows thereby providing aregular pattern of apertures. Core elements are placed on the base platewith an integral projection of each core extending into the aperture.Fasteners are then placed at each aperture, on the opposite side of thebase plate to firmly hold each core in place. The pattern of coresextending from the other side of the base plate thus assumes the patternof the apertures described above. This type of mold results in muchflexibility of changing patterns, or details of the mold when desired bypermitting the cores and end plates to be changed as desired.

Also, according to the present invention, end plates are connected tothe edges of the base plate to form walls around the sides of the baseplate to prevent flow of casting material off the base plate. At leastone of these end plates includes a plurality of interior projections toform one half of a row of cores to facilitate matching abutting sectionsof the product to be cast thereon. Any number of the sides of the baseplate may be provided with such end plates, depending upon the number ofsides of the cast product which must be matched and abutted to form acontinuous pattern.

Preferably, the individual cores are of an inexpensive material such asplastic, for example, polypropylene or nylon. The cores preferably havesome degree of flexibility and are precision-molded. The cores aretightened against the base plate by the fasteners, which may preferablybe self-threading screws. Such cores may then be replaced or repaired bysimple operation. The cores are tightened by means of the screws so thatno flashing will occur between the base plate and the bottom surface ofthe cores.

In the drawings which illustrate a specific embodiment of the invention:

FIG. 1 is a plan view of a casting mold according to our invention;

FIG. 2 is a section view taken substantially along line 2-2 of FIG. 1;

FIG. 3 is an enlarged plan view of the end plate of the casting mold;

FIG. 4 is a section view taken along line 4-4 of FIG. 3; and

FIG. 5 is a partial plan view of sections of a continuous belt molded inaccordance with this invention.

Referring to the drawings, there is illustrated one embodiment of theinvention including a rectangular base plate 10 having a multiplicity ofholes 12 drilled therein in a regular pattern. The base plate may be ofa material such as metal having the ability to withstand moldingtemperatures in the order of 300F. Holes 12 are formed in a plurality ofparallel, equally spaced rows R R R and R,,, each having a plurality ofequally spaced holes 12. Alternate rows R R R and R,, are also equallyspaced and contain a plurality of equally spaced holes 12 therein. Therows of holes, and holes within adjacent rows are staggered so that aregular pattern of equally spaced holes are provided in base plate 10.In the embodiment illustrated, two opposite ends are provided with plainend bars 16 and 18 defining boundaries of the casting areas. End plates16 and 18 are secured to opposite end plates 20 and 22 by studs 24, 26,28 and 30. Opposite end plates 20 and 22 are secured to base plate 10 bymeans of studs 34, 36, 38 and 40.

Throughout the entire span between end plates 16, 18, 20 and 22, aplurality of plugs or core members 32 are provided so as to result in aspecific design or configuration for the molding surface. The shape ofthe core members 32 are best shown in FIGS. 3 and 4. The

core members 32 include a body portion 50 of hexagonal geometric shapewhen viewed in plan, and of upwardly and inwardly tapering shape whenviewed in elevation. The body portion 50 is provided with a shank 52centered at its base for extending through the aperture 12 in base platefor connecting to a fastener, illustrated as being a self-threadingscrew 54. By firmly tightening the screw 54, the shank 52, and thus thebase of the body 50 is caused to be pulled into tight contact withsurface 58 of plate 10, thereby minimizing the possibility of a spaceexisting betweensurface 58 and the base of the body portion 50. Thisconstruction virtually eliminates flashing around the base of the bodyportion 50.

The core member 32 also includes an axially extending, upwardly taperingpin 60 for introducing an aperture in the belt section to be molded. Thepin 60 is slightly flexible, and joins the body portion 50 in a slightcircumferential flare at 62. Flexibility of pin 60 and the flare at 62greatly aid in stripping a molded object from the base plate, andprevent rupturing of intricate details of the molded object. Each of thecore members 32 are set in angular alignment, so as to form aninterconnected network of voids 70 to be filled in by the moldingmaterial. The core members 32 may conveniently be a durable,injection-molded plastic material.

Significant advantages are realized by the use of specially designed endplates and 22. These end plates are provided with spaced half-sectionsof core members 72 at equal intervals across two sides of the mold inthe embodiment illustrated. The half-sections adjacent row R are mirrorimages of the closest half-sections of row R and provide continuity ofthe voids 70 up to the very edge of the mold. Thus, when molded sectionsare placed in abutting relationship, the pattern is exactly continuous.Of course, any number of the ends may be made by the use of such an endplate according to the design of the belt to be molded. For example, ifthe belt is to be two sections in width, three sides will be molded withthe special end plates. If the belt is only to be a single section inwidth, it is only necessary for the special end bars to be used on twoends.

The parts of the casting mold described herein are readily removable andreplacable so that damaged parts can be replaced with very littleexpense and inconvenience. Also, easy interchangeability is permitted sothat the pattern of the casting can easily be changed. For example, thecore elements 32 and the end plates 20 and 22 can all be changed toresult in a new pattern if desired.

In FIG. 5, there is illustrated a partial perspective view of aproduction mold made in accordance with this invention. This mold isformed with an interconnected grid of wall portions 80 generallyperpendicular to the plane of the top and bottom of the mold. The

wall portions 80 define the boundaries of adjacent cells 82 and areformed by the continuous voids 70 of the casting mold. The cells 82 areformed by the core elements 32, and the holes 84 are formed by pins 60or the core elements. From FIG. 5, it may be seen that the border 86 ofthe mold is formed by half-sections of cells 88, by means of the spacedhalf-sections of the core members 72. Another section ofmold, formed ina similar manner, may be exactly matched to this edge 86 to form acontinuous pattern of the interconnected grid and cells 82.

EXAMPLE SILASTIC E RTV Mold-Making Rubber, a silicone rubber product ofDow-Corning Corporation, is cast to make a female production hexagonstructured mold as follows:

1. 6 pounds of rubber is mixed with 0.6 pound (10 percent) thinner andblended thoroughly with a spatula, taking care not to whip air into theblend.

2. A solution of 5 to 15 percent petroleum jelly in methylene chlorideis poured over a metal and polypropylene core male mold, insuring allcores have been wet by the solution. The mold is then drainedthoroughly, leaving a thin film of petroleum jelly on all mold surfaces.The excess methylene chloride is allowed to evaporate (within one-halfhour at room temperature, or it may be flashed off in an oven atl30-l60l=. in 3 to 5 minutes).

3. The casting mold is then set in a large oven/vacuum chamber andleveled to insure even flow of the silicone rubber when poured in.

. The 0.6 pound of rubber thinned with 10 percent inert thinner(SILASTIC RTV THINNER, a product of Dow-Corning Corporation) is thencatalyzed with 6 pounds of SILASTIC E RTV Catalyst, a product ofDow-Corning Corporation, in the same manner the thinner was mixed in.This solution will remain pourable for up to 2 hours before extensivecuring takes place.

5. The thinned, catalyzed rubber is placed in vacuum desicators (becauseof the amount of rubber and the size of the desicators, 2 are used forthis application), and 28-30 inch Hg vacuum is drawn to de-air thesolution. Immediately, the rubber expands to four or five times itsoriginal volume as the initial air is drawn off, then the level of thesolutions falls to its original height. This process takes 4 to 6minutes. The rubber is then sufficiently deaerated to be poured.

6. The rubber is poured into the casting mold in the oven (not turned onat this point), taking care to completely cover all core elements to alevel even with the half-hexagon cut end plates. Two steel plates, heldflush to the base plate with C-clamps, retain the rubber on the othertwo mold edges.

7. The top is placed on the oven/vacuum chamber,

and the rubber in the mold is deaerated again with 27-29 inch vacuum.The vacuum is pulled for 10 to 15 minutes until bubbles appear all overthe rubber surface. The oven is then vented, collapsing the bubbles andinducing flow into the voids where the air comes out of solution. Vacuumis pulled again for 15 minutes and then the chamber is vented.

8. Heaters in the oven/vacuum chamber are now turned on, with athermostat set at F. The air pressure is atmospheric. The rubber willcure completely in 2 hours. The heaters are turned off, the oven plate(top) is raised, and the mold is allowed to cool.

9. When the mold has cooled sufiiciently that it may be picked up, it isthen taken to a freezer at 0F. and left for 1 to 2 hours to reachthermal equilibrium. It is then removed and the silicone rubberproduction female mold is pulled gently from the casting mold. Silasticrubber adhesive will repair any tears which may occur.

The invention has been described in considerable detail with particularreference to certain preferred embodiments thereof, but it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention.

We claim:

1. A mold for casting a flexible piece of material, said mold having aregular pattern of depressions defined by surrounding side walls, andthe land area of said walls defining an interconnected grid comprising:

a. a base plate,

b. a plurality of core members provided on said base plate in a regularpattern of parallel rows, the core members in each row beingsubstantially equally spaced, and the core members in alternate rowsbeing staggered with respect to the core members in adjacent rowsthereby providing a regular, interconnected network of spaces betweencore members, and

. end plates attached to the sides of said base plate defining theboundaries of said mold, said end plates having spaced, inwardlyprotruding halfcore members in staggered relation with the core membersin the adjacent first row of core members mounted on said base plate,

. said core members having a surface for firmly contacting said baseplate at their junction therewith to prevent flashing of the materialbeing molded, and having bases and integral pins extending from thebases to form apertures in the material being molded, said pins joiningsaid bases in a circumferential flare at the junction thereof.

2. A mold according to claim 1 in which said core members are detachablymounted on said base plate.

3. A mold according to claim 1 in which said core members are of amaterial having the ability to flex slightly upon application of force.

4. A mold according to claim 1 in which said core members taper slightlyin a direction away from said base plate.

1. A mold for casting a flexible piece of material, said mold having aregular pattern of depressions defined by surrounding side walls, andthe land area of said walls defining an interconnected grid comprising:a. a base plate, b. a plurality of core members provided on said baseplate in a regular pattern of parallel rows, the core members in eachrow being substantially equally spaced, and the core members inalternate rows being staggered with respect to the core members inadjacent rows thereby providing a regular, interconnected network ofspaces between core members, and c. end plates attached to the sides ofsaid base plate defining the boundaries of said mold, said end plateshaving spaced, inwardly protruding half-core members in staggeredrelation with the core members in the adjacent first row of core membersmounted on said base plate, d. said core members having a surface forfirmly contacting said base plate at their junction therewith to preventflashing of the material being mOlded, and having bases and integralpins extending from the bases to form apertures in the material beingmolded, said pins joining said bases in a circumferential flare at thejunction thereof.
 2. A mold according to claim 1 in which said coremembers are detachably mounted on said base plate.
 3. A mold accordingto claim 1 in which said core members are of a material having theability to flex slightly upon application of force.
 4. A mold accordingto claim 1 in which said core members taper slightly in a direction awayfrom said base plate.